Discharge tube



May 6, 1930;

C. BOL bIS'CHARGE TUBE Filed Sept 30 1924 Patented May 6 1930 I UNITEDSTATES'PATENT OFFICE CORNEIJIS BOL, OF EINDHOVEN, NETHERLANDS, ASSIGNOR,BY MESNE ASSIGNMENTS,

TO RADIO CORPORATION OF AMERICA, OF NEW YORK,

NEW YORK N. Y., A CORPORATION" OF DISCHARGE TUBE Application filedSeptember 30, 1924, Serial No. 740,738, and in the Netherlands October17, 1923.

- This invention has reference to incandescent cathode discharge tubes,especially to discharge tubes of the said kind, the operation of whichis essentially based on elec- 5 tronic motion.

In incandescent cathode discharge tubes in which the electric dischargetakes place practically entirely or essentially by electronic motion, orin other words in which positive 10 ionization does not practicallyoccur or only to a very little extent, the electrons are deflected fromthe course they would follow exclusively under the influence of theelectric field by the action of the magnetic field arising around thecurrent carrying incandescent wire. This phenomenon becomes particularlyimportant when the discharge tube is intended for very great capacitiesand in this connection the diameter of the incandescent wire becomeslarge, for example materially over 1 millimetre. I

If for example in a high vacuum rectifier which contains a straightlystretched incandescent wire and a cylindricalanode coaxially arrangedtherewith a voltage is supplied between the incandescent cathode and theanode, the electrons emitted by the incandescent wire would moveradially from the incandescent wire to the anode if they were notdeflected from that course by the magnetic field surrounding theincandescent wire. By reason of this deflection it is essential that thevoltage supplied between the anode and the cathode should lie beyond acertain a do not reach the anode but return to the incandescent wire.

When the thickness of the incandescent wire becomes considerable and in.this connection the incandescent current very heavy, the said deflectionmay become so large'that difiiculty is encountered in constructing thetube, as the minimum value referred to of the voltage. becomes high andcomes to lie beyond the intended voltage of operation.

The invention has for its object to cause the magnetic field referred toto disappear or at least to materially weaken the same by a particularconstruction of the cathode 5 and also to insure a very solidarrangement minimum value as otherwise the electrons of the incandescentcathode coaxially with other cylindrical electrodes.

In discharge tubes according to the inventron the incandescent cathodeconsists of a tube inside of which is a conductor, the tube and theconductor being so shaped and arranged relatively to each other that themagnetic fields generated by currents of equal strength and flowing inthe tube and in the conductor in opposite directions neutralize or atleast materially weaken each other outside the tube. The conductorprovided within the tube may consist of one or more wires.

According to the inventionmeans may be provided for cooling theconductor.

The incandescent cathode accordingto the invention may preferablyconsist of a tube having an annular cross-section, a conductor beingsubstantially coaxially arranged inside said tube, the tube and theconductor being at one end in conductive connection with each other.

According to the invention the conductor in the tubular incandescentcathode may be The rectifier shown on the drawing conformed into atubular aggregate. The incandescent cathode may be superficially coatedwith substances that easily emit electrons, for'example, with one ormore oxides of material, prefthealkaline earth metals and the tubeitself may in this case be constructed of material having a lowermelting point than tungsten, such for example as platinum or nickel.

The tube 1 is on one side in conductive connection with a conductor 3.For, this purpose the conductor may at that place be provided with aflared out or expanded portion 2 which is sealed-to the tubular cathode.The conductor 3 is substantially coaxially arranged in the tube and mayconsist of material which is a good conductor of electricity, such forexample as nickel or copper. It will however frequently be essential toalso make the conductor 3 of tungsten. The conductor 3 and the tube 1must be adapted to carry a current of e ual strength. The crosssectionof the con uctor 3 is chosen that the temperature of t e latter duringthe operation of the tube remains lower than of thetubular cathode 1.The conductor 3 is clas ed within a binary strap 4: as indicated inigure 1, which strap may consist of nickel and is connected in any wayfor example by soldering, to two metal caps 5 hermeticall sealed at theedge to the ends of glass tu es 6. Thecaps 5 have fixed to themleading-inwires 7. Suitable material forthe said caps is chrome iron ofsuch composition thatits coeflicient of expansion corresponds to that ofthe glass. When using for example potassium soda glass, the content ofchromium may be about 17 to 20%. On the other side of the caps 5 aresecured-the leadin -in wires-7.

he tubular incandescent cathode 1 is clasped within a binary strap 8secured to two caps 9, which in their turn have fixed to them leading-inwires 10. The'caps are hermetically sealed t6 glass tubes 11 and mayconsist for example 0 chrome iron of suitable composition. The glasstubes 11 and the tube 5 form part of a glass sealing member 12 which atthe edge is hermetically sealed to the end of avessel 13 serving as ananode. This vessel may at the place of sealing consist of chrome iron ofsuitable. composition, and preferably the entire vessel is made ofchrome iron. The vessel 13 is cylindrical and coaxially arrangedrelatively to the incandescent cathode 1. It is provided with a thread14 by means of which the discharge tube'can be located in a vesselthrough which a cooling'liquid for thejan'ode 13 flows.

' The conductor 3 shewn in Fi re 2 is made hollow and has arrangedinside a tube of small diameter'15 for t e supply of the cooling medium.The conductor 3may in this case be connected directly to a ca 16 whichhas fixed to it a leading-in wire 1%. In this case the leadin -in wire17should'be hollow so as to allow or the passage of the tube 15.

It is obvious that with the constructions of the incandescent cathodeaccording to the invention shewn on thedr'awing, no magnetic referablyso fields arise outside the incandescent cathode and that consequentlythe electrons'under the influence of the electric field prevailingbetween the incandescent cathode and the anode will move at leastapproximately radially.

I claim: 4

1. A discharge tube having a tubular incandescent cathode, a hollowconductor disposed substantially coaxially within said tubular cathode,said conductor and said tubular cathode being at one end connection witheach other, and means for cooling the said hollow conductor.

2. A discharge tube having a cylindrical anode member forming a portionof the outside wall of said tube, a base portion for said tube and an.air-tight connection between said base portion and said anode member, atubular cathode member extendin coaxially of said anode member containedwithin' said tube closed by said anode member, means for supporting saidtubular cathode within said tube and rigidly fastening the same,connections for supplying current to said tubular cathode passingthrough said support means,

and base member, a second tubular member contained within said tubularcathode and in conductive relationship therewith at one end, and meansfor rigidly mounting said second tubular member within said cathode andestablishing a current connection therewith, said tubular'cathode andsaid inner conducting tube providing means for neutralizing magneticfields produced by current flowing through said members wherebyelectronic emission takes place in a radial direction between saidcathode and anode.

3. In a discharge vessel, a cylindrical anode member, a glass supportmeans for said anode of like diameter to said anode, means forhermetically'sealing said glass support means and said cylindrical anodeto form'an evacuated envelope, a tubular cathode supported within saidcylindrical anode andarranged coaxially with respect thereto, aplurality of connections between said glass support member and saidgathode for supplying current to said cathode and rigidly mounting thesame, a tubular member within said cathode for completing the cathodecircuit and permitting currents to flow therethrough in an oppositedirection to the direction of flow through said cathode,

in conductive Ill means for establishing electrical connection with saidinner tubular member, "means for rlgidly supporting said last namedmember from said glass support, and a' connection between said tubularcath- ,ode and said inner tubular member at theend of each member remotefrom said support members, said tubular cathode and inner tubular memberproviding means whereby currents flowing t erethrough produce magneticfields in opposite directions so that the field outside said tubularcathode is neutralized and electronic emission takes place between saidcathode and said anode in a radial direc-. tion. s

4. In an electronic discharge arrangement, a glass supporting memberforming a base for the discharge apparatus, a tubular anode member, saidmember being of like cross-sectional size to said glass support memberand means for fastening said glass support member to said anode andproviding an hermetim cally sealed body, a tubular cathode within saidhermetically sealed body, a binary strap carried by said glass supportfor rigidly mounting said tubular cathode coaxially with respectto saidanode, means for sealing said strapto said glass support, said strapproviding means for establishing a current connec-. tion for saidtubular cathode, a second binary stra supported from said glass support,and

a tubular member carried thereby and rigidly supported within saidtubular cathode, said tubular member and said cathode being inconductive relationship with respect to each other at the end remotefrom said support, said cathode and inner tubular member providing meansfor producing opposing ma net-ic fields external to said tubular catho eupon a flow of current therethrough, whereby the magnetic field externalto said cathode is neutralized and electronic emission takes place inradial direction from said cathode to said anode.

v 5. The arrangement claimed in claim 4 comprising, in addition, atubular cooling member contained within said last named tubular memberand means for introducing a cooling fluid within said coolin member formaintainin said tubular memger contained within sai cathode at atemperature below that of said tubular, cathode.

o In testimony whereof I 'aflix my signature, atthe city 0 Eindhoven,this 3rd day of September, A. D. 1924. 7

' CORNELIS BOL.

